Page 82 - Plastics Engineering

Mechanicd Behaviour of Plastics 65

Therefore

1 x 10"

- 8.5 MN/m2
P= - -

n( 0.25 ) (30) (5

The nylon ring may be considered as a duck wall cylinder subjected to this

internal pressure (see Appendix D). At the inner surface of the ring there will

be a hoop stress, uo, and a radial stress, crrm Benham et al. shows these to be

Hoop stress, cr,, = p { ;}

Radial stress, or = -p

where k = ratio of outer to inner radius.

Hence the hoop strain, 80, at the bore of the ring is given by

SO

kZ + 1

E

This is the interference needed on radius to give the desired separation force.

(b) To facilitate easy assembly, the nylon should be heated so that the inner

radius expands by his mount. As shown in the previous section

0.32

-
AT= -. .- -214'C

100 x x 15

(c) The maximum stress in the nylon ring when it is on the shaft will be the

hoop stress at the bore. This is given by

k2 + 1

00 = p